Transcription is the production of an RNA transcript from DNA. In eukaryotic cells, transcription takes place in the nucleus.
The process of transcription
- The DNA in the region containing the required gene unwinds, breaking hydrogen bonds between complementary bases and exposing the base sequences.
- One of the exposed DNA strands is used as the template strand; the other is the non-template strand.
- Free RNA nucleotides form hydrogen bonds with complementary bases on the template strand. In RNA, uracil is used instead of thymine.
- RNA polymerase joins neighbouring RNA nucleotides by forming phosphodiester bonds, building the sugar–phosphate backbone of the RNA molecule.
- After the gene has been copied, the RNA transcript detaches. Hydrogen bonds reform between complementary DNA bases so the DNA returns to its double-stranded form.
Exam Tip: In an explanation of transcription, identify the template DNA strand, describe complementary base pairing of RNA nucleotides and state that RNA polymerase joins the RNA nucleotides.